U.S. patent number 7,106,478 [Application Number 10/055,003] was granted by the patent office on 2006-09-12 for image processing device and method for controlling the same.
This patent grant is currently assigned to Kabushiki Kaisha Toshiba, Toshiba Tec Kabushiki Kaisha. Invention is credited to Gaku Takano.
United States Patent |
7,106,478 |
Takano |
September 12, 2006 |
Image processing device and method for controlling the same
Abstract
An image input module inputs image signals which have different
sampling rates. Based on a predetermined processing flow, a filter
processing module carries out a filter processing by a
predetermined filter factor on the image signals which are inputted
by the image input module. A plurality of filter factors which are
used at the filter processing module are set at a filter factor
setting module. A filter factor selecting module selects, from
among a plurality of filter factors, an appropriate filter factor
in accordance with the sampling rates of the image signals and the
processing flow, and supplies them to the filter processing
module.
Inventors: |
Takano; Gaku (Yokohama,
JP) |
Assignee: |
Kabushiki Kaisha Toshiba
(Tokyo, JP)
Toshiba Tec Kabushiki Kaisha (Tokyo, JP)
|
Family
ID: |
27609182 |
Appl.
No.: |
10/055,003 |
Filed: |
January 25, 2002 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20030142372 A1 |
Jul 31, 2003 |
|
Current U.S.
Class: |
358/3.26;
358/1.9; 382/260; 382/274 |
Current CPC
Class: |
G06T
5/20 (20130101); H04N 1/0402 (20130101); H04N
1/4092 (20130101); G06T 5/002 (20130101); G06T
2207/10008 (20130101) |
Current International
Class: |
H04N
1/407 (20060101) |
Field of
Search: |
;358/3.26,1.9
;382/260,274,168 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Tran; Douglas Q.
Assistant Examiner: Worku; Negussie
Attorney, Agent or Firm: Foley & Lardner LLP
Claims
What is claimed is:
1. An image processing device comprising: a raster scanning type
image input module which reads images from a document and outputs
image signals indicating the images, at different sampling rates;
and a filter processing module which performs filter processing on
the image signals output from the raster scanning type image input
module, wherein: the raster scanning type image input module
outputs, in synchronism with an image clock, a first or second
image signal read at a preset sampling rate or a sampling rate
higher than the preset sampling rate in a main scanning direction
and a sub-scanning direction of the document, when a sampling rate
of reading of the document is switched by an external sampling rate
selection signal and the sampling rate selection signal is in a low
sampling rate mode or a high sampling rate mode, the raster
scanning type image input module also outputting a
main-scanning-directional image effective signal when the first or
second image signal is output; the filter processing module
includes a line memory controller supplied with the first or second
image signal output from the raster scanning type image input
module, the main-scanning-directional image effective signal, and
the image clock, a plurality of line memories connected to the line
memory controller, an image window section connected to the line
memory controller, a filter computing section connected to the
image window section, a selector connected to the filter computing
section, and serving as a filter factor selecting module, a filter
factor 1 setting section connected to the selector and serving as a
filter factor setting module, and a filter factor 2 setting section
connected to the selector and serving as a filter factor setting
module, the filter factor selecting module selecting either the
filter factor 1 setting section or the filter factor 2 setting
section in accordance with the sampling rate selection signal; the
line memory controller sequentially stores the first or second
image signal, output from the raster scanning type image input
module, into the line memories in units of lines in accordance with
the main-scanning-directional image effective signal, reads image
data of (W.times.H) pixels around a to-be-processed pixel,
including the to-be-processed pixel, from the first or second image
signal, stored in the line memories, in accordance with the image
clock, and outputs the image data to the image window section,
whereby the image window section latches the image data of
(W.times.H) pixels output from the line memory controller, the
latched image data being output to the filter computing section;
the filter computing section multiplies each piece of the image
data by a filter factor output from the selector as the filter
factor selecting module, using a corresponding one of multipliers,
and sums up resultant data pieces using a total adding machine; a
total value output from the total adding machine is expressed as a
numerical value of (.+-.m, n), m being an integer of m bits, n
being a decimal fraction of n bits, (.+-.m, n) being accordingly
(m+n+1) bits; and the total value is converted into an integer by
an integrator and output as a filter processing result of an
integer of m bits.
2. The image processing device according to claim 1, wherein the
filter factor selected by the selector as the filter factor
selecting module and used during the filter processing is used for
switching a cutoff frequency.
3. The image processing device according to claim 2, wherein the
filter factor selected by the selector as the filter factor
selecting module and used during the filter processing is used for
making a cutoff frequency corresponding to the first image signal
lower than a cutoff frequency corresponding to the second image
signal.
4. The image processing device according to claim 2, wherein: the
filter factor selected by the selector as the filter factor
selecting module and used during the filter processing is used for
making a cutoff frequency corresponding to the first image signal
lower than a frequency acquired by subtracting a main frequency
component of an input image signal from twice a vector indicating a
Nyquist frequency during processing of the first image signal; and
the filter factor is used for making a cutoff frequency
corresponding to the second image signal lower than a main
frequency of the input image signal.
5. The image processing device according to claim 2, wherein: the
filter factor selected by the selector as the filter factor
selecting module and used during the filter processing is used for
making a cutoff frequency corresponding to the first image signal
lower than a frequency acquired by subtracting a number of screen
lines contained in the document and providing the first image
signal, from twice a vector indicating a Nyquist frequency during
processing of the first image signal; and the filter factor is used
for making a cutoff frequency corresponding to the second image
signal lower than the number of the screen lines contained in the
document.
6. An image processing device comprising: raster scanning type
image input means for reading images from a document and outputting
image signals indicating the images, at different sampling rates;
and filter processing means for performing filter processing on the
image signals output from the raster scanning type image input
means, wherein: the raster scanning type image input means outputs,
in synchronism with an image clock, a first or second image signal
read at a preset sampling rate or a sampling rate higher than the
preset sampling rate in a main scanning direction and a
sub-scanning direction of the document, when a sampling rate of
reading of the document is switched by an external sampling rate
selection signal and the sampling rate selection signal is in a low
sampling rate mode or a high sampling rate mode, the raster
scanning type image input means also outputting a
main-scanning-directional image effective signal when the first or
second image signal is output; the filter processing means includes
a line memory controller supplied with the first or second image
signal output from the raster scanning type image input means, the
main-scanning-directional image effective signal, and the image
clock, a plurality of line memories connected to the line memory
controller, an image window section connected to the line memory
controller, a filter computing section connected to the image
window section, a selector connected to the filter computing
section and serving as filter factor selecting means, a filter
factor 1 setting section connected to the selector and serving as
filter factor setting means, and a filter factor 2 setting section
connected to the selector and serving as filter factor setting
means, the filter factor selecting means selecting either the
filter factor 1 setting section or the filter factor 2 setting
section in accordance with the sampling rate selection signal; the
line memory controller sequentially stores the first or second
image signal, output from the raster scanning type image input
means, into the line memories in units of lines in accordance with
the main-scanning-directional image effective signal, reads image
data of (W.times.H) pixels around a to-be-processed pixel,
including the to-be-processed pixel, from the first or second image
signal, stored in the line memories, in accordance with the image
clock, and outputs the image data to the image window section,
whereby the image window section latches the image data of
(W.times.H) pixels output from the line memory controller, the
latched image data being output to the filter computing section;
the filter computing section multiplies each piece of the image
data by a filter factor output from the selector as the filter
factor selecting means, using a corresponding one of multipliers,
and sums up resultant data pieces using a total adding machine; a
total value output from the total adding machine is expressed as a
numerical value of (.+-.m, n), m being an integer of m bits, n
being a decimal fraction of n bits, (.+-.m, n) being accordingly
(m+n+1) bits; and the total value is converted into an integer by
an integrator and output as a filter processing result of an
integer of m bits.
7. The image processing device according to claim 6, wherein the
filter factor selected by the selector as the filter factor
selecting means and used during the filter processing is used for
switching a cutoff frequency.
8. The image processing device according to claim 7, wherein the
filter factor selected by the selector as the filter factor
selecting means and used during the filter processing is used for
making a cutoff frequency corresponding to the first image signal
lower than a cutoff frequency corresponding to the second image
signal.
9. The image processing device according to claim 7, wherein: the
filter factor selected by the selector as the filter factor
selecting means and used during the filter processing is used for
making a cutoff frequency corresponding to the first image signal
lower than a frequency acquired by subtracting a main frequency
component of an input image signal from twice a vector indicating a
Nyquist frequency during processing of the first image signal; and
the filter factor is used for making a cutoff frequency
corresponding to the second image signal lower than a main
frequency of the input image signal.
10. The image processing device according to claim 7, wherein: the
filter factor selected by the selector as the filter factor
selecting means and used during the filter processing is used for
making a cutoff frequency corresponding to the first image signal
lower than a frequency acquired by subtracting a number of screen
lines contained in the document and providing the first image
signal, from twice a vector indicating a Nyquist frequency during
processing of the first image signal; and the filter factor is used
for making a cutoff frequency corresponding to the second image
signal lower than the number of the screen lines contained in the
document.
11. A control method for an image processing device comprising:
preparing raster scanning type image input means; reading images
from a document and outputting image signals indicating the images,
at different sampling rates, using the raster scanning type image
input means; preparing filter processing means: performing filter
processing on the image signals output from the raster scanning
type image input means, using the filter processing means, wherein:
the raster scanning type image input means outputs, in synchronism
with an image clock, a first or second image signal read at a
preset sampling rate or a sampling rate higher than the preset
sampling rate in a main scanning direction and a sub-scanning
direction of the document, when a sampling rate of reading of the
document is switched by an external sampling rate selection signal
and the sampling rate selection signal is in a low sampling rate
mode or a high sampling rate mode, the raster scanning type image
input means also outputting a main-scanning-directional image
effective signal when the first or second image signal is output;
the filter processing means includes a line memory controller
supplied with the first or second image signal output from the
raster scanning type image input means, the
main-scanning-directional image effective signal, and the image
clock, a plurality of line memories connected to the line memory
controller, an image window section connected to the line memory
controller, a filter computing section connected to the image
window section, a selector connected to the filter computing
section and serving as filter factor selecting means, a filter
factor 1 setting section connected to the selector and serving as
filter factor setting means, and a filter factor 2 setting section
connected to the selector and serving as filter factor setting
means, the filter factor selecting means selecting either the
filter factor 1 setting section or the filter factor 2 setting
section in accordance with the sampling rate selection signal; the
line memory controller sequentially stores the first or second
image signal, output from the raster scanning type image input
means, into the line memories in units of lines in accordance with
the main-scanning-directional image effective signal, reads image
data of (W.times.H) pixels around a to-be-processed pixel,
including the to-be-processed pixel, from the first or second image
signal, stored in the line memories, in accordance with the image
clock, and outputs the image data to the image window section,
whereby the image window section latches the image data of
(W.times.H) pixels output from the line memory controller, the
latched image data being output to the filter computing section;
the filter computing section multiplies each piece of the image
data by a filter factor output from the selector as the filter
factor selecting means, using a corresponding one of multipliers,
and sums up resultant data pieces using a total adding machine; a
total value output from the total adding machine is expressed as a
numerical value of (.+-.m, n), m being an integer of m bits, n
being a decimal fraction of n bits, (.+-.m, n) being accordingly
(m+n+1) bits; and the total value is converted into an integer by
an integrator and output as a filter processing result of an
integer of m bits.
12. The control method according to claim 11, wherein the filter
factor selected by the selector as the filter factor selecting
means and used during the filter processing is used for switching a
cutoff frequency.
13. The control method according to claim 12, wherein the filter
factor selected by the selector as the filter factor selecting
means and used during the filter processing is used for making a
cutoff frequency corresponding to the first image signal lower than
a cutoff frequency corresponding to the second image signal.
14. The control method according to claim 12, wherein: the filter
factor selected by the selector as the filter factor selecting
means and used during the filter processing is used for making a
cutoff frequency corresponding to the first image signal lower than
a frequency acquired by subtracting a main frequency component of
an input image signal from twice a vector indicating a Nyquist
frequency during processing of the first image signal; and the
filter factor is used for making a cutoff frequency corresponding
to the second image signal lower than a main frequency of the input
image signal.
15. The control method according to claim 12, wherein: the filter
factor selected by the selector as the filter factor selecting
means and used during the filter processing is used for making a
cutoff frequency corresponding to the first image signal lower than
a frequency acquired by subtracting a number of screen lines
contained in the document and providing the first image signal,
from twice a vector indicating a Nyquist frequency during
processing of the first image signal; and the filter factor is used
for making a cutoff frequency corresponding to the second image
signal lower than the number of the screen lines contained in the
document.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image processing device and a
method for controlling the same, and in particular, to an image
processing device and a method for controlling the same which
employ a technique which is applied to filter processing in an
image processing section of an image forming device, such as a
color image copier or the like, which handles image signals of
different sampling rates.
2. Description of the Related Art
In a conventional color image copier, three-channel image signals
such as RGB signals are read out by a charge coupled device (CCD)
or the like at the same sampling rate, and are processed in an
image processing section at a latter stage.
Thus, at a filter included in the image processing section,
frequency characteristics, such as a cut-off frequency and the
like, which are appropriate for only that sampling rate are
set.
Moreover, when a line sensor (CCD), which outputs image signals of
plural channels having different sampling rates, is used as image
input means, a Nyquist frequency changes in accordance with the
sampling rate. Thus, functions such as elimination of moire and the
like cannot be realized with the same filter factor.
In particular, when an image, to which a screen (dots) has been
applied, is inputted such as a document manuscript by dot printing,
at a time of a low sampling rate, the Nyquist frequency is lower
than the screen frequency. Sampling is carried out with a periodic
configuration of the manuscript image being bent back with the
Nyquist frequency in the center.
On the other hand, at a time of a high sampling rate, there are
cases in which the Nyquist frequency is higher than the frequency
of the periodic configuration of the input image (the number of dot
lines of the printed manuscript).
In this way, when the Nyquist frequency changes in accordance with
the sampling rate of the input image signal, at the filter
processing section, functions such as the elimination of moire and
the like cannot be realized when filter processing is carried out
at the same filter factor. Thus, a separate, excessive un-sharpness
processing is required, and the problem arises that this is not
always preferable from the standpoint of cost performance.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide an image
processing device and a method for controlling the same, in order
to overcome the above-described problematic points, by making it
possible to select a filter factor which has appropriate frequency
characteristics in accordance with the sampling rate and a
processing flow of an input image signal, thus moire can be
suppressed without the need for an excessive un-sharpness
processing.
In order to achieve the above-described object, according to a
first aspect of the present invention, there is provided an image
processing device comprising:
an image input module which inputs image signals having different
sampling rates;
a filter processing module which, based on a predetermined
processing flow, carries out filter processing by a predetermined
filter factor on the image signals which are inputted by the image
input module;
a filter factor setting module at which a plurality of filter
factors which are used in the filter processing module are set;
and
a filter factor selecting module which selects, from among the
plurality of filter factors at the filter factor setting module, an
appropriate filter factor in accordance with the sampling rates of
the image signals which are inputted by the image input module and
a processing flow at the filter processing module, and supplies
them to the filter processing module.
Further, according to a second aspect of the present invention,
there is provided an image processing device according to the first
aspect in which the filter processing by the predetermined filter
factor at the filter processing module is linear filter processing,
and
the filter factor selecting module selects, as the appropriate
filter factor, a filter factor to switch a filter frequency
characteristic in the linear filter processing by the filter
processing module.
Further, according to a third aspect of the present invention,
there is provided an image processing device according to the
second aspect in which a filter factor to switch the filter
frequency characteristic which is selected by the filter factor
selecting module is a filter factor to switch a cutoff
frequency.
Further, according to a fourth aspect of the present invention,
there is provided an image processing device comprising:
an image input module which inputs a first image signal having a
predetermined sampling rate and a second image signal having a
sampling rate which is higher than the sampling rate of the first
image signal;
a filter processing module which, based on a predetermined
processing flow, carries out linear filter processing by a
predetermined filter factor on the first and second image signals
which are inputted by the image input module;
a filter factor setting module at which a plurality of filter
factors which are used in the filter processing module are set;
and
a filter factor selecting module which selects, from among the
plurality of filter factors at the filter factor setting module, as
a filter factor in linear filter processing by the filter
processing module, an appropriate filter factor in accordance with
the sampling rates of the first and second image signals which are
inputted by the image input module and a processing flow at the
filter processing module, and supplies them to the filter
processing module.
Further, according to a fifth aspect of the present invention,
there is provided an image processing device according to the
fourth aspect in which the filter factor in the linear filter
processing which is selected by the filter factor selecting module
is a filter factor to switch a cutoff frequency.
Further, according to a sixth aspect of the present invention,
there is provided an image processing device according to the fifth
aspect in which the filter factor in the linear filter processing
which is selected by the filter factor selecting module is a filter
factor to make a cutoff frequency for the first image signal lower
than a cutoff frequency for the second image signal.
Further, according to a seventh aspect of the present invention,
there is provided an image processing device according to the fifth
aspect in which the filter factor in the linear filter processing
which is selected by the filter factor selecting module is a filter
factor
to make a cutoff frequency for the first image signal lower than a
frequency in which a main frequency component of an inputted image
signal is subtracted from twice a vector which expresses a Nyquist
frequency at a time of processing the first image signal, and
to make a cutoff frequency for the second image signal lower than
the main frequency of the inputted image signal.
Further, according to a eighth aspect of the present invention,
there is provided an image processing device according to the fifth
aspect in which the filter factor in the linear filter processing
which is selected by the filter factor selecting module is a filter
factor
to make a cutoff frequency for the first image signal lower than a
frequency in which a number of screen lines of a manuscript which
presents the first image signal is subtracted from twice a vector
which expresses a Nyquist frequency at a time of processing the
first image signal, and
to make a cutoff frequency for the second image signal lower than
the number of screen lines of the manuscript.
Further, according to a ninth aspect of the present invention,
there is provided an image processing device comprising:
image input means for inputting image signals having different
sampling rates;
filter processing means for carrying out, based on a predetermined
processing flow, a filter processing by a predetermined filter
factor on the image signals which are inputted by the image input
means;
filter factor setting means at which a plurality of filter factors
which are used in the filter processing means are set; and
filter factor selecting means for selecting, from among a plurality
of filter factors at the filter factor setting means, an
appropriate filter factor in accordance with the sampling rate of
the image signal which is inputted by the image input means and a
processing flow at the filter processing means, and for supplying
them to the filter processing means.
Further, according to a tenth aspect of the present invention,
there is provided an image processing device according to the ninth
aspect in which the filter processing by the predetermined filter
factor at the filter processing means is a linear filter
processing, and
the filter factor selecting means selects, as the appropriate
filter factor, a filter factor to switch a filter frequency
characteristic in the linear filter processing by the filter
processing means.
Further, according to a eleventh aspect of the present invention,
there is provided an image processing device according to the tenth
aspect in which the filter factor to switch the filter frequency
characteristic which is selected by the filter factor selecting
means is a filter factor to switch a cutoff frequency.
Further, according to a twelfth aspect of the present invention,
there is provided an image processing device comprising:
image input means for inputting a first image signal having a
predetermined sampling rate and a second image signal having a
sampling rate which is higher than the sampling rate of the first
image signal;
filter processing means for carrying out, based on a predetermined
processing flow, a linear filter processing by a predetermined
filter factor on the first and second image signals which are
inputted by the image input means;
filter factor setting means at which a plurality of filter factors
which are used in the filter processing means are set; and
filter factor selecting means for selecting, from among the
plurality of filter factors at the filter factor setting means and
as a filter factor in the linear filter processing by the filter
processing means, an appropriate filter factor in accordance with
the sampling rates of the first and second image signals which are
inputted by the image input means and a processing flow at the
filter processing means, and for supplying them to the filter
processing means.
Further, according to a thirteenth aspect of the present invention,
there is provided an image processing device according to the
twelfth aspect in which the filter factor in the linear filter
processing which is selected by the filter factor selecting means
is a filter factor to switch a cutoff frequency.
Further, according to a fourteenth aspect of the present invention,
there is provided an image processing device according to the
thirteenth aspect in which the filter factor in the linear filter
processing which is selected by the filter factor selecting means
is a filter factor to make a cutoff frequency for the first image
signal lower than a cutoff frequency for the second image
signal.
Further, according to a fifteenth aspect of the present invention,
there is provided an image processing device according to the
thirteenth aspect in which the filter factor in the linear filter
processing which is selected by the filter factor selecting means
is a filter factor
to make a cutoff frequency for the first image signal lower than a
frequency in which a main frequency component of an inputted image
signal is subtracted from twice a vector which expresses a Nyquist
frequency at a time of processing the first image signal, and
to make a cutoff frequency for the second image signal lower than
the main frequency of the inputted image signal.
Further, according to a sixteenth aspect of the present invention,
there is provided an image processing device according to the
thirteenth aspect in which the filter factor in the linear filter
processing which is selected by the filter factor selecting means
is a filter factor
to make a cutoff frequency for the first image signal lower than a
frequency in which a number of screen lines of a manuscript which
presents the first image signal is subtracted from twice a vector
which expresses a Nyquist frequency at a time of processing the
first image signal, and
to make a cutoff frequency for the second image signal lower than
the number of screen lines of the manuscript.
Further, according to a seventeenth aspect of the present
invention, there is provided a method for controlling an image
processing device which carries out a filter processing on an image
signal which is inputted, the method comprising:
inputting image signals having different sampling rates;
carrying out, based on a predetermined processing flow, a filter
processing by a predetermined filter factor on the image
signals;
setting a plurality of filter factors which are used in the filter
processing; and
selecting, from among the plurality of filter factors, an
appropriate filter factor in accordance with the sampling rates of
the image signals and a processing flow, and supplying them to the
filter processing.
Further, according to a eighteenth aspect of the present invention,
there is provided a method for controlling an image processing
device according to the seventeenth aspect in which the filter
processing by the predetermined filter factor is linear filter
processing, and
a filter factor to switch a filter frequency characteristic in the
linear filter processing is selected as the appropriate filter
factor in the filter processing.
Further, according to a nineteenth aspect of the present invention,
there is provided a method for controlling an image processing
device according to the eighteenth aspect in which the filter
factor to switch the filter frequency characteristic is a filter
factor to switch a cutoff frequency.
In order to achieve the above-described object, according to a
twentieth aspect of the present invention, there is provided a
method for controlling an image processing device which carries out
a filter processing on an image signal which is inputted, the
method comprising:
inputting a first image signal having a predetermined sampling rate
and a second image signal having a sampling rate which is higher
than the sampling rate of the first image signal;
carrying out, based on a predetermined processing flow, a linear
filter processing by a predetermined filter factor on the first and
second image signals;
setting a plurality of filter factors which are used in the linear
filter processing; and
selecting, from among the plurality of filter factors, as a filter
factor in the linear filter processing, an appropriate filter
factor in accordance with the sampling rates of the first and
second image signals and the processing flow, and supplying them to
the linear filter processing.
Further, according to a twenty-first aspect of the present
invention, there is provided a method for controlling an image
processing device according to the twentieth aspect in which the
filter factor in the linear filter processing is a filter factor to
switch a cutoff frequency.
Further, according to a twenty-second aspect of the present
invention, there is provided a method for controlling an image
processing device according to the twenty-first aspect in which the
filter factor in the linear filter processing is a filter factor to
make a cutoff frequency for the first image signal lower than a
cutoff frequency for the second image signal.
Further, according to a twenty-third aspect of the present
invention, there is provided a method for controlling an image
processing device according to the twenty-first aspect in which the
filter factor in the linear filter processing is a filter factor to
make a cutoff frequency for the first image signal lower than a
frequency in which a main frequency component of an inputted image
signal is subtracted from twice a vector which expresses a Nyquist
frequency at a time of processing the first image signal, and
to make a cutoff frequency for the second image signal lower than
the main frequency of the inputted image signal.
Further, according to a twenty-fourth aspect of the present
invention, there is provided a method for controlling an image
processing device according to the twenty-first aspect in which the
filter factor in the linear filter processing is a filter factor to
make a cutoff frequency for the first image signal lower than a
frequency in which a number of screen lines of a manuscript which
presents the first image signal is subtracted from twice a vector
which expresses a Nyquist frequency at a time of processing the
first image signal, and to make a cutoff frequency for the second
image signal lower than the number of screen lines of the
manuscript.
CORRESPONDING EMBODIMENTS
The first, ninth, and seventeenth aspects of the present invention
in the above correspond to a first embodiment and a modified
example of the first embodiment which will be described later.
Further, the second, tenth, and eighteenth aspects of the present
invention in the above correspond to the first embodiment which
will be described later.
Further, the third, eleventh, and nineteenth aspects and the fifth,
thirteenth, and twenty-first aspects of the present invention in
the above correspond to a third modified example of a second
embodiment which will be described later.
Further, the fourth, twelfth, and twentieth aspects of the present
invention in the above correspond to the first embodiment and the
second embodiment which will be described later.
Further, the sixth, fourteenth, and twenty-second aspects of the
present invention in the above correspond to a second modified
example of the second embodiment which will be described later.
Further, the seventh, fifteenth, and twenty-third aspects of the
present invention in the above correspond to the second modified
example of the second embodiment which will be described later.
Further, the eighth, sixteenth, and twenty-fourth aspects of the
present invention in the above correspond to a first modified
example of the second embodiment which will be described later.
Additional objects and advantages of the invention will be set
forth in the description which follows, and in part will be obvious
from the description, or may be learned by practice of the
invention. The objects and advantages of the invention may be
realized and obtained by means of the instrumentalities and
combinations particularly pointed out hereinafter.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
The accompanying drawings, which are incorporated in and constitute
a part of the specification, illustrate presently preferred
embodiment of the invention, and together with the general
description given above and the detailed description of the
preferred embodiment given below, serve to explain the principles
of the invention.
FIG. 1 is a block diagram showing a schematic configuration of
first and second embodiments of an image processing device of the
present invention;
FIG. 2 is a diagram showing a schematic configuration of an image
data window section of FIG. 1;
FIG. 3 is a diagram showing a schematic configuration of a filter
factor 1 setting section of FIG. 1;
FIG. 4 is a diagram showing a schematic configuration of a filter
computing section of FIG. 1;
FIG. 5 is an amplitude characteristic graph which is expressed by a
schematic normalized frequency to explain operations of the first
embodiment of the image processing device of the present
invention;
FIG. 6 is an amplitude characteristic graph which is expressed by
an actual frequency to explain operations of the first embodiment
of the image processing device of the present invention; and
FIG. 7 is an amplitude characteristic graph which expresses a
cutoff which considers bending back at the time of a low sampling
rate, to explain operations of the second embodiment of the image
processing device of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Reference will now be made in detail to the presently preferred
embodiments of the invention as illustrated in the accompanying
drawings, in which like reference numerals designate like or
corresponding parts.
Hereinafter, embodiments of an image processing device of the
present invention will be described with reference to the
figures.
FIRST EMBODIMENT
FIG. 1 is a block diagram showing a schematic configuration in
accordance with a first embodiment of the image processing device
of the present invention.
The image processing device is configured from a raster scanning
type image input module 11 which reads and outputs an image of an
unillustrated manuscript at different sampling rates, and a filter
processing module 12 which carries out a filter processing on the
image signal which is inputted by the raster scanning type image
input module 11.
At the raster scanning image input module 11, the sampling rate at
the time of reading an image of a manuscript is switched by a
sampling rate selection signal SAM1 from the exterior.
Here, the raster scanning type image input module 11 reads the
image of the manuscript at a main scanning sampling rate of 600 dpi
and a sub-scanning sampling rate of 600 dpi, when SAM1=0 (high
sampling rate mode).
Further, the raster scanning type image input module 11 reads the
image of the manuscript at a main scanning sampling rate of 300 dpi
and a sub-scanning sampling rate of 300 dpi, when SAM1=1 (low
sampling rate mode).
The raster scanning type image input module 11 synchronizes, with
an image clock CLK, image data FLTIN (8 bits) of the manuscript
which is read in the aforementioned high sampling rate mode or low
sampling rate mode, and outputs them to the filter processing
module 12.
In the raster scanning type image input module 11, while an image
signal of the same line is being outputted, a main scanning
direction image effective signal HDEN=0. When the output line is
incremented, HDEN=1, and thereafter, HDEN=0 again in accordance
with the output of the next line, and these operations are
repeated.
The filter processing module 12 is configured from a line memory
controller 13 to which the read image data FLTIN (8 bits) from the
raster scanning type image input module 11, the main scanning
direction image effective signal HDEN, and the image clock CLK are
supplied; a plurality of (1-N) line memories 14 which are connected
to the line memory controller 13; an image window section 15 which
is connected to the line memory controller 13; a filter computing
section 19 which is connected to the image data window section 15;
a selector 18 which serves as a filter factor selecting module and
which is connected to the filter computing section 19; and a filter
factor 1 setting section 16 and a filter factor 2 setting section
17 which serve as filter factor setting modules and which are
connected to the selector 18.
Here, the line memory controller 13 stores the read image data
(image signal) FLTIN from the raster scanning type image output
module 11 in the plurality of (1-N) line memories 14 successively
for each line, in accordance with the main scanning direction image
effective signal HDEN.
In this way, the latest read image data of the Nth line among the
read image data from the raster scanning type image output module
11 is always held in the line memory 14 (the latest data is entered
in the Nth line).
Further, the line memory controller 13 reads out the image data of
W.times.H (pixels) with the pixel in the center, which is the
object of processing, in accordance with the image clock CLK, from
the image data stored in the plurality of (1-N) line memories 14
and outputs these to the image data window section 15.
Here, the image data of the W.times.H (pixels), which are outputted
from the line memory controller 13, are latched to the image data
window section 15, and the image data is outputted to the filter
computing section 19.
Here, operations will be described supposing that the image data
window section 15 is 13.times.13 (pixels) and that the number of
the plurality (1-N) of line memories 14 is 14.
FIG. 2 is a diagram showing a schematic configuration of the image
data window section 15.
In this case, at the image data window section 15, the 13 pixels
from P0,0 to P0,12 are arranged in the main scanning direction, and
the 13 pixels from P0,0 to P0,12 are arranged in the sub-scanning
direction.
FIG. 2 shows a case in which the image data of the pixel which is
the object of processing is stored in the center pixel of interest
P6,6, and the image data of the W.times.H (pixels) surrounding the
pixel which is the object of processing are stored in the
respective pixels from P0,0 to P12,12.
FIG. 3 is a diagram showing a schematic configuration of the filter
factor 1 setting section 16.
Namely, a filter factor 1 of 7.times.7=49 elements is respectively
stored in the filter factor 1 setting section 16 (the same is
performed for the filter factor 2 setting section 17) in order to
make the filter processing have bend-back symmetry in the main
scanning direction and the sub-scanning direction with the
aforementioned pixel of interest in the center.
In this case, at the filter factor 1 setting section 16 and the
filter factor 2 setting section 17, respectively, the 7 elements
from h0,0 to h0,6 are arranged in the main scanning direction, and
the 7 elements from h0,0 to h0,6 are arranged in the sub-scanning
direction.
FIG. 3 shows a case in which, in correspondence with the image data
window section 15, the filter factor of the image data of the pixel
which is the object of processing is stored in the element of
interest h6,6, and the filter factors of the image data surrounding
the pixel which is the object of processing are stored in the
respective elements from h0,0 to h6,6.
FIG. 4 is a diagram showing a schematic configuration of the filter
computing section 19 of FIG. 1.
Namely, as shown in FIG. 4, when the read image data (image signal)
from the raster scanning type image output module 11 is a high
sampling rate (SAM1=0), the respective elements of the filter
factor h0,0 to h6,6 (here, respectively .+-.7.5 bits) which
correspond to the filter factor 1 setting section 16 are selected
via the respective selectors 18 by the sampling rate selection
signal SAM1, and are outputted from the respective selectors
18.
Further, when the read image data (image signal) from the raster
scanning type image output module 11 is a low sampling rate
(SAM1=0), the respective elements of the filter factor from g0,0 to
g6,6 (here, respectively .+-.7.5 bits) which correspond to the
filter factor 2 setting section 17 are selected via the respective
selectors 18, and are outputted from the respective selectors
18.
In the filter computing section 19, as shown in FIG. 4, after the
respective image data and the filter factors (here, respectively
.+-.7.5 bits) from the respective selectors 18 are multiplied by
respective multipliers M, the total sum is calculated by a total
adding machine S.
In this case, considering the symmetry of the respective pixels of
13.times.13 in the image data window section 15 shown in FIG. 2,
the respective image data is supplied to the respective multipliers
M as 10 bits or 9 bits each by respective partial adding machines s
determining the partial sums of the 36 sets of P0,0, P0,12, P12,0,
P12,12, . . . P5,5, P5,7, P7,5, P7,7, and the 6 sets of P0,6,
P12,6, . . . P5,6, P7,0, and the 6 sets of P6,0, P6,12, . . . P6,5,
P6,7, each formed by 8 bits.
Further, the 1 set of P6,6 formed by 8 bits is supplied to the
multiplier M.
Thus, the total sum value from the total adding machine S is
expressed as a (.+-.m, n) signed decimal number.
Here, the integer number is m bits, the decimal number is n bits,
and as a whole m+n+1 bits.
Due to this total sum value from the sum adding machine S (here,
.+-.23.5 bits) being made to be an integer (rounded-off) by an
integrator I, it becomes the integer m bits (here, 8 bits) by being
clipped to 0 through 255. Thereafter, it is outputted as a filter
processing result FLOUT.
Here, in order to simplify the explanation, the filter factor which
does not consider bend back symmetry of the filter factor 1 setting
section 16, is f1 (n1, n2), where n1=0, 1 . . . 12, and n2=0, 1 . .
. 12.
Similarly, the filter factor of the filter factor 2 setting section
17 is f2 (n1, n2), where n1=0, 1 . . . 12, and n2=0, 1 . . .
12.
Further, a frequency characteristic H1 of the filter when the
filter factor 1 setting section 16 is selected is expressed by
expression (1):
.times..function.e.pi..times..times..omega..times..times.e.pi..omega..tim-
es..times..function.e.pi..times..times.e.pi..times..times..times..times..t-
imes..function..times.e.pi..times..times..omega.e.pi..times..times..omega.-
.function.e.pi..times..times..omega..times..times.e.pi..omega..times..time-
s..times.e.theta..function..omega..times..times..omega..times..times.
##EQU00001##
where, |H1(e.sup.j.pi..omega.x, e.sup.j.pi..omega.y)| is a term
expressing the amplitude characteristic,
e.sup.j.theta.1(.omega.x, .omega.y) is a term expressing the phase
characteristic,
.omega.x is a main scanning normalized frequency, and .omega.x=-1
to 1,
.omega.y is a sub-scanning normalized frequency, and .omega.y=-1 to
1,
fNx1 is a main scanning Nyquist frequency, and is 1/2 of the main
scanning sampling rate, and
fNy1 is a sub-scanning Nyquist frequency, and is 1/2 the
sub-scanning sampling rate.
In the same way, frequency characteristic H2 of the filter when the
filter factor 2 setting section 17 is selected is expressed by
expression (2):
.times..function.e.pi..times..times..omega..times..times.e.pi..omega..tim-
es..times..function.e.pi..times..times.e.pi..times..times..times..times..t-
imes..function..times.e.pi..times..times..omega.e.pi..times..times..omega.-
.function.e.pi..times..times..omega..times..times.e.pi..omega..times..time-
s..times.e.theta..function..omega..times..times..omega..times..times.
##EQU00002##
where, |H2(e.sup.j.pi..omega.x, e.sup.j.pi..omega.y)| is a term
expressing the amplitude characteristic,
e.sup.j.theta.2 (.omega.x, .omega.y) is a term expressing the phase
characteristic,
.omega.x is a main scanning normalized angular frequency, and
.omega.x=-1 to 1,
.omega.y is a sub-scanning normalized angular frequency, and
.omega.y=-1 to 1,
fNx2 is the main scanning Nyquist frequency, and is 1/2 of the main
scanning sampling rate, and
fNy2 is the sub-scanning Nyquist frequency, and is 1/2 of the
sub-scanning sampling rate.
Note that the main scanning normalized angular frequency .omega.x
and the sub-scanning normalized angular frequency .omega.y may be
expressed as -1.ltoreq..omega.x, .omega.y.ltoreq.1,
respectively.
Further, if the main scanning sampling rate and the sub-scanning
sampling rate at the time of a high sampling rate are respectively
expressed by fSx1 and fSy1, the Nyquist frequencies are fNx1=fSx1/2
and fNy1=fSy1/2, respectively.
Similarly, if the main scanning sampling rate and the sub-scanning
sampling rate at the time of a low sampling rate are respectively
expressed by fSx2 and fSy2, the Nyquist frequencies are fNx2=fSx2/2
and fNy2=fSy2/2, respectively.
Based on the preceding examples, at the time of a high sampling
rate,
fSx1=600 (cpi), fNx1=300 (cpi)
fSy1=600 (cpi), fNy1=300 (cpi)
Further, at the time of a 1ow samp1ing rate,
fSx2=300 (cpi), fNx2=150 (cpi)
fSy2=300 (cpi), fNy2=150 (cpi)
Given that the Nyquist frequencies are (fNx, fNy), the following
relational equations are established between the normalized angular
frequencies .omega.x, .omega.y) and the actual frequencies (fx, fy)
on the image which is read by the input system.
(.omega.x, .omega.y)=(fx/fNx, fy/fNy)
(fx, fy)=(fNx*.omega.x, fNy*.omega.y)
Accordingly, when the filter factor 1 and the filter factor 2 have
the same factor, as shown in the equation (1) and the equation (2),
from the standpoint of the normalized angular frequency, the
frequency characteristics coincide, but from the standpoint of the
actual frequency, they are different due to the influence of the
Nyquist frequency.
FIG. 5 shows, at this time, the amplitude characteristic by two
filter factors when the frequency characteristic is considered in a
one-dimensional direction and the normalized angular frequency is
the abscissa.
FIG. 6 shows, at this time, the amplitude characteristic by two
filter factors when the frequency characteristic is considered in a
one-dimensional direction and the actual frequency is the
abscissa.
As can be understood from FIG. 6, because peak frequencies and the
like of the filter factor 1 and the filter factor 2 are different,
a difference arises between the sharpness of the images which are
processed.
Here, in the present invention, the filter factor 1 setting section
16 and the filter factor 2 setting section 17 which are different
from each other are prepared. The setting is switched between the
setting of the filter factor 1 and the setting of the filter factor
set 2, used in accordance with the switching of the sampling rate.
Thus a desired sharpness function and the like are realized.
Note that, in the above, explanation is given of the filter
processing of image data of any one line of RGB as the read image
data from the raster scanning type image output module 11.
In actuality, the filter processing is carried out by appropriately
switching between the setting of the filter factor 1 and the
setting of the filter factor 2 per one line of image data of each
RGB in accordance with the sampling rate of the read image data and
a predetermined processing flow per one line of image data of each
RGB as the read image data.
Further, when the same read manuscript is read simultaneously at
different sampling rates and the filter processing is carried out
at each signal channel, it suffices that the filter processing,
which corresponds to the sampling rates shown in the present
embodiment, is carried out for each channel.
MODIFIED EXAMPLE OF THE FIRST EMBODIMENT
The first embodiment as described above has been described by using
the frequency characteristic as an example. However, as a modified
example of the first embodiment, other than in a linear filter, for
example, in a sequence filter or the like, by switching the
sampling number (filter characteristic) in accordance with the
sampling rate, effects such as a deterioration in the noise
eliminating ability due to a change in the sampling rate or the
like can be mitigated.
SECOND EMBODIMENT
Next, an image processing device of a second embodiment of the
present invention will be described.
Note that, because the main configurations of the second embodiment
are similar to those of the first embodiment shown in FIG. 1,
description thereof is omitted.
In a printed photograph or an image outputted by a printer or the
like, there is a periodic component (called a main frequency
component) in the high frequency, other than the frequency
component that is generated by a contrast of the original image or
the like.
The frequency of the frequency component is (fpx, fpy), and
fp=.parallel.(fpy, fpx).parallel..sub.--2. (Namely, the absolute
value of the main frequency component is, for convenience, called
the main frequency component.)
Note that, .parallel.a.parallel..sub.--2 means square norm sqrt
(a^2)
In the present embodiment, the main frequency component is a design
parameter, and determines the frequency characteristic of the
filter factor 1 and the frequency characteristic of the filter
factor 2.
Here, the frequency whose amplitude characteristic is substantially
zero (for example, 5% or less) is called the cutoff frequency
fc.
Since the amplitude characteristic is for a two-dimensional
frequency, it means that the amplitude characteristic is
substantially zero in the range which is .parallel.(fx,
fy).parallel..sub.--2>=fc.
In the present embodiment, a cutoff frequency fc2 of the amplitude
characteristic of the filter factor 2 at the time of a low sampling
rate is determined by the following expression (3) by the Nyquist
frequencies (fNx2, fNy2) and (fpx, fpy). fc2<.parallel.(2*fNx2-i
fpx, 2*fNy2-fpy).parallel..sub.--2 (3)
Further, a cutoff frequency fcl of the amplitude characteristic of
the filter factor 1 at the time of a high sampling rate is
determined by the following expression (4) by the Nyquist
frequencies (fpx, fpy). fc1<.parallel.(fpx,
fpy)>.parallel..sub.--2 (4)
The effects of the present embodiment will be described by using
the case of (fpx, fpy)=(175 (cpi), 0) as an example.
FIG. 7 shows the amplitude characteristics and the like of the
filter factor 1 and the filter factor 2 in the main scanning
direction which are determined by the present embodiment.
Since the Nyquist frequency at the time of a low sampling rate is
fNx2=150 cpi, the frequency component of (fpx, fpy) is bent back at
the Nyquist frequency at the time of sampling other than the
Nyquist frequency, and is shown as a peak of (2*fNx2-fpx,
2*fNy2-fpy) on the image signal.
Since the cutoff frequency fc2 of the filter factor 2 at the time
of a low sampling rate satisfies the conditions of the expression
(3), the peak is eliminated by the filter processing.
On the other hand, because the Nyquist frequency fNx1=300 cpi at
the time of a high sampling rate, bending-back does not occur.
Further, because the cutoff frequency fc1 of the filter factor 1
satisfies the expression (4), the peak component can be
eliminated.
Namely, in the present embodiment, due to filters which satisfy the
expression (3) and the expression (4) being switched in accordance
with the sampling rate and processing being carried out, the main
frequency component can be eliminated.
In this way, when the main frequency component is eliminated,
interference moire, which easily arises when some periodic
processing (for example, system dither processing) is carried out
in the subsequent stage of filter processing, can be
suppressed.
Further, when the same read manuscript is read simultaneously at
different sampling rates and the filter processing is carried out
at the respective signal channels, it suffices that the filter
processing which corresponds to the sampling rate which is shown in
the present embodiment is carried out for each channel.
FIRST MODIFIED EXAMPLE OF THE SECOND EMBODIMENT
Further, in the second embodiment as described above, the main
frequency component is (fpx, fpy). However, as a first modified
example of the second embodiment, it suffices that the number of
screen lines of the manuscript image is used instead of the main
frequency component (fpx, fpy) in the filter processing relating to
read image data of a manuscript which is screen-printed.
SECOND MODIFIED EXAMPLE OF THE SECOND EMBODIMENT
Further, in the second embodiment as described above, the
conditions of the expression (3) and the expression (4) were given
in relation to the setting of the cutoff frequency. However, there
are cases when there are a plurality of main frequency components,
or when (fpx, fpy) is indefinite.
Thus, as a second modified example of the second embodiment, in
such cases, the condition is looser than those of the expression
(3) and the expression (4). If the filter factor is set under the
condition of fc2<fc1 (5) it is effective for cases when the
conditions of the expression (3) and the expression (4), which are
shown in the above-described second embodiment, are automatically
satisfied.
THIRD MODIFIED EXAMPLE OF THE SECOND EMBODIMENT
Further, in the second embodiment as described above, the effect of
changing the cutoff frequency was described from the standpoint of
eliminating moire. However, when a manuscript such as a character
manuscript or the like in which priority is given to the
resolution, image quality is improved more when the cutoff
frequency fc2 at the time of a low sampling rate is set to be as
high as possible.
On the other hand, at the time of a high sampling rate, there is
the need to cut off the extremely high region of the high frequency
region due to problems such as the S/N ratio or the like.
Thus, as a third modified example of the second embodiment, in this
case, simply, a configuration in which the cutoff frequency is
switched according to the sampling rate is effective.
Therefore, according to the present invention as described above,
it is possible to provide an image processing device and a method
for controlling the same in which, due to the filter factor, which
has an appropriate frequency characteristic, being able to be
selected according to the sampling rate of the input image signal
and the processing flow, moire can be suppressed without requiring
excessive un-sharpness processing.
Additional advantages and modifications will readily occur to those
skilled in the art. Therefore, the invention in its broader aspects
is not limited to the specific details and representative
embodiments shown and described herein. Accordingly, various
modifications may be made without departing from the spirit or
scope of the general inventive concept as defined by the appended
claims and their equivalents.
* * * * *